As will be appreciated, sails for use in sailing vessels are configured to accommodate different wind conditions. For instance, when a vessel is running with the wind, it is typical to provide as a foresail, a spinnaker which is either full cut or asymmetrically cut. The purpose of the spinnaker is to drive the vessel forward at maximum speed by catching the wind which is coming from astern or abaft the beam. In this sailing condition, the vessel is said to be running either dead down wind or on a broad reach. Spinnakers are most useful in these types of wind conditions, but are also useful, depending on the wind velocity, for beam reaches in which the wind is coming perpendicular to the beam of the vessel.
However, running or reaching, one wishes to come into the wind, such as for tacking purposes, then the apparent wind direction changes from a beam reach at 90 degrees to as little as 28 degrees for genoa jibs, which are properly configured and set. When the vessel either changes direction or the wind changes direction relative to the vessel, sail changes are required, especially the foresail, in order to adapt to the changing wind condition. The result is that a spinnaker, if used, needs to be doused, and a genoa jib or other jib raised, to accommodate a change from a downwind run or reach to a position where the vessel is hard on the wind. Sail changes are tedious and time consuming, and require a number of foredeck personnel to effectuate the change. The change is accompanied by the un-attaching and re-attaching of jib sheets, guys and halyards. The inconvenience of sail changing not only affects the cruising sailor, but also is critical in sailboat racing.
More particularly, with respect to sail vessel racing, the racing rules sometimes specify that only a limited number of sails may be carried for a particular race. It is therefore desirable to have the ability to be able to effectuate a sail change by reshaping the sail that is already up, so as to be within the rules for the particular race.
Additionally, in order to assist in simplifying the flying of a spinnaker, so-called asymmetric spinnakers have been developed, sometimes called genakkers, in which the tack of the sail is fixed to a bowsprit or boom ahead of the vessel, with the sail being hoisted by a halyard at the head of the sail, and with the jib sheet being attached to the clew of the sail. When running with the wind, these asymmetric spinnakers billow forwardly of the vessel and provide a large amount of sail presented to the wind to drive the vessel hard. This provides full performance at broad wind angles and limited apparent wind speed, which is the wind speed on the sail while the vessel is sailing. These asymmetric spinnakers are effective running down wind or on broad reaches, and are still somewhat effective at beam reaches. However, the vessel cannot be made to point closer than about 90 degrees to the wind before the leading edge or luff of the sail begins to collapse and drive is lost. It is at this apparent wind angle of about 90 degrees that the asymmetric spinnaker is doused in favor of a traditional genoa jib or working jib, thus requiring a sail change as the vessel rounds up into the wind.
It is therefore desirable to have a system which permits a single sail to be used in a wide variety of wind conditions, from running with the wind, all the way to a close reach.